In operation maintenance of a wireless network, causes of interruption occurring in wireless links can be broadly categorized as being either a drop in reception power due to effects of an obstacle or the like (worsening of the radio wave propagation environment), or an increase in radio wave interference. However, determining the inference cause when interruption occurs in a wireless link requires knowledge and experience. There is accordingly a need for automatic determination of the interruption cause employing received signal strength indicator (RSSI) and a packet error rate (PER), these being general parameters that evaluate wireless link performance. Satisfying this need would enable the burden of operation maintenance for wireless networks to be reduced.
Technology related to the above has been proposed in which, for cases in which the packet loss rate (packet error rate) is a threshold value or above, the cause of the interruption is determined to be a worsening of the radio wave propagation environment when an evaluation value for the radio wave reception strength is the threshold value or less, and the cause of the interruption is determined to be radio wave interference when the evaluation value for the radio wave reception strength is greater than the threshold value. In this technology, as illustrated in FIG. 10, coordinate space of the packet error rate against radio wave reception strength is divided into four quadrants by a threshold value of radio wave reception strength 150 and a threshold value of the packet error rate 152. A second quadrant is set as a region for determining that the radio wave propagation environment has worsened, and a first quadrant is a region is set as a region for determining that there is radio wave interference.